Endless belt seed crystal gripping and pulling means

ABSTRACT

Crystal-growing apparatus comprising a crystal-pulling mechanism in the form of a carriage mounted for vertical movement relative to a melt-containing crucible, a pair of endless belts carried by the carriage and arranged to grip an elongate crystalline body issuing from the melt, and means for moving either the carriage or the endless belts to effect pulling of the crystalline body.

United States Patent Seymour Mermelstein [72] Inventor 2,927,008 Shockley 2 3/301 SP Newton, Mass. 3,055,741 9/1962 Maclnnis.... 1 23/273 SP [21] Applv No. 809,731 3,144,308 8/1964 Tarter 23/301 SP [22} Filed Mar. 24, 1969 3,494,742 2/1970 Kuba et aL. 23/273 SP (45] Patented Sept. 21,1971 3,515,836 6/1970 Kallas 23/273 SP [73] Assignec Tyco Laboratories, Inc. FOREIGN PATENTS v Mass 584,866 4 1931 Germany 226/172 Primary Examiner--Norman Yudkoff [54] ENDLESS BELT SEED CRYSTAL GRlPPlNG AND Ass/slam Edwards PULLING MEANS AttrneyNicholas A. Pandiscio 27 Claims, Drawing Figs.

52 vs. 01 23/273 s1 23/301 SP, 226/172, 148/l.6

Crystal g owing apparatus comprising a crystal- [50] Field of Search 23/273 SP, pulling mechanism in the f f a Carriag mounted f m- 301 SP; 148/1.6 22 /17 18] cal movement relative to a melt-containing crucible, a pair of endless belts carried by the carriage and arranged to grip an [56] References cued elongate crystalline body issuing from the melt, and means for UNITED STATES PATENTS moving either the carriage or the endless belts to effect pulling 2,647,699 8/1953 Bush 226/172 X of the crystalline body.

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PATENTEU SEP21 1971 SHEET 2 [IF 6 ATTORNEY.

PATENTEDSEPZI mm W 3 BF 6 350m 12 illllllll lllllljl SFYMOUI? MfRMElSTE/N INVENTOR.

ATTORNEY.

PATENTEU SEPZI l9?! SHEET 5 OF 6 SEYMOUR MfR/l/IHSTf/N INVENTOR.

ATTORNEY.

PATENTED SEF21 |97l 3607112 SHEET 8 [IF 6 288%- 13a POWER SUPPLY MOTOR BELT I46 292 6 CLUTCH BRAKE A/ I 302 BRAKE J 304 1 FIG. 7. W06

i L CARRIAGE CLUTCH 298 i 142 I l l SEYMOUR Mf/PMHSTf/N I N VE N TQR.

ATTORNEY.

ENDLESS BELT SEED CRYSTAL GRIPPING AND PULLING MEANS This invention relates generally to a novel furnace combination for the growth of elongate crystals from melts of appropriate materials.

Conventional apparatus is available for producing a crystal of solid material from a melt, such apparatus comprising a furnace adapted to accommodate a crucible containing a source material which is maintained as a melt, and means for contacting the surface of the melt with a seed and slowly withdrawing the seed at a rate-and under conditions such that a portion of the melt solidifies on the seed. By appropriately maintaining the operating conditions, a crystal of considerable length can be grown on the seed. Such conventional apparatus suffers from certain limitations well known to persons skilled in the art, particularly with respect to the ability to (a) grow crystals in short or extended lengths or (b) grow a thin continuous filament characterized by uniform size and straightness.

Accordingly it is a principal object of this invention to provide a new and improved apparatus for growing selected crystalline shapes such as filaments, ribbons, etc., in short or extended lengths. 1

A further object is to provide apparatus adapted for growing thin continuous crystalline filaments from a melt, such apparatus being adapted to operate so as to yield a product that is straight and has a uniform size.

A further object is to provide a crystal-growing apparatus which is rugged, simple in construction, safe and reliable in operation, adapted for growth of different shapes, and embodies a novel crystal-pulling mechanism whose mode of operation is adjustable to permit controlled growth of crystals in short or extended lengths.

Still another object is to provide a novel crystal-pulling mechanism which is adapted for two alternative modes of operation.

The foregoing objects and other objects hereinafter described or rendered obvious are achieved by an apparatus which may be briefly described as comprising means for supporting a crucible containing a supply of source material in solid form, means for heating the crucible to convert the source material to a melt, and a crystal-pulling mechanism which includes a carriage mounted for vertical movement relative to the crucible, means for raising the carriage, moveable crystal gripping and pulling means mounted on the carriage, and means for preventing movement of the crystal gripping and pulling means as the carriage is being raised and for causing operating movement of the gripping and pulling means when said carriage is stationary, whereby a crystal issuing from the crucible can be pulled by movement of the carriage or by operating movement of the gripping and pulling means. The apparatus also includes means for effecting sequential movement of the carriage and the moveable gripping means so that growing crystal is pulled first by movement of said carriage and then by operating movement of said gripping means. A further feature is the provision of means for varying the maximum height to which the carriage can be raised relative to the crucible.

Other features and many of the attendant advantages of the invention are presented in the following detailed description which is to be considered together with the accompanying drawings wherein:

FIG. 1 is a vertical front elevation of a preferred embodiment of the invention, with the drive and crystal-gripping assemblies of the pull mechanism omitted for the sake of clarity;

FIG. 2 is a vertical side elevation of the apparatus shown in FIG. 1;

FIG. 3 is a plan view on an enlarged scale of the drive assembly of the pull mechanism;

FIG. 4 is a side elevation of the drive mechanism shown in FIG. 3;

FIG. 5 is a side elevation, partly in section, on an enlarged scale of the crystal-gripping assembly of the pull mechanism;

FIG. 6 is a front view in elevation of the crystal-gripping assembly shown in FIG. 5;

FIG. 7 is a block diagram showing one form of control system for the pull mechanism;

FIG. 8 is a fragmentary front elevation of a modification of the crystal-gripping assembly;

FIG. 9 is a view taken along line 99 of FIG. 8; and

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9.

Turning now to FIGS. 1 and 2, the illustrated embodiment comprises a rigid bed 2 supported by a plurality of upstanding legs 4. The bed 2 has three spaced holes 8 (only one is shown in detail in the drawings) to accommodate three like vertically extending rods 10, 12 and 14, and also an enlarged opening 16 (the purpose of which is hereinafter described). Mounted on the upper ends of rods l0, l2 and 14 is a rigid horizontal plate 18. Another plate 19 is similarly secured to the bottom ends of the same rods. Plates l8 and 19 serve to tie the three rods together as a unitary assembly.

Mounted on the bed 2 is a plate 20 having a large opening 22 which is aligned with the opening 18, plus three additional holes 24 which are aligned with the openings 8 in the bed 2.

Positioned in each of the holes 24 and secured to the plate 20 is an annular sleeve 26 having a tapered inner surface 28. Mounted within each of the sleeves 26 is a bushing 30 whose exterior surface is tapered so as to mate with the adjacent tapered surface 28 of the sleeve 26. Each bushing 30 is secured in place by means of screws 34 which screw into tapped holes formed by mating cavities in the bushing and the surrounding sleeve 26. The bushings 30 are fabricated so as to make snug sliding fits with the rods 10, 12 and 14. In effect the sleeves 26 and the bushings 30 form clamping ring assemblies for the rods. When the bolts 34 are loosened the rods can slide within the bushings. When the bolts are screwed up tight, the bushings are forced downward into the sleeves 26 and, by virtue of their conically tapered mating surfaces, at wedging effect is produced which compresses the bushings tightly around the rods 10, 12 and 14. This releasable clamping arrangement makes it possible to raise or lower the three rods and top plate 18 to different positions relative to the bed 2 and to lock the rods in a selected position.

Supported by the plate 20 is a furnace indicated generally by the numeral 36. It is to be understood that the exact form of the furnace may vary and also that the construction of the furnace 36 is simplified in FIGS. 1 and 2 for convenience of illustration and description. Essentially the furnace comprises an elongate hollow member surrounded by an RF. heating unit 38. The latter is energized by a suitable power source (not shown) which is adjustable to vary the rate of heating. The fur nace defines a crucible heating chamber open at both ends. Furnace 36 is provided with end fittings 40 and 42. The bottom end fitting 40 is attached to a mounting ring 44 that is secured to the plate 20. The furnace 36 is aligned with openings 18 and 22. The upper end fitting 42 is attached to a horizontally extending brace plate 46 which is secured to rods 10 and 12 by suitable clamping members 48 which are attached to the brace plate by screws 50. The brace plate 46 has an opening located so as to permit introduction of a seed to the furnace. The brace plate 46 and clamping members 48 are shaped so that portions of their confronting surfaces form holes with diameters close to those of the rods 10 and 12, so that tightening screws 50 serves to clamp plate 46 and members 48 to the rods. From the foregoing description it is believed to be apparent that the furnace 36 is then locked against movement at both ends and that the brace plate 46 must be first unclamped from the rods 10 and 12 when the height of the latter is to be changed.

The crucible from which the crystal is to be grown is introduced to furnace 36 via its bottom end. This is achieved by means of a crucible carriage identified generally by the numeral 56 which is slidably mounted on rods 10 and 12. The crucible carriage comprises a horizontal plate 58 having openings which are fitted with slide bearings 60 which are mounted on rods 10 and 12. The slide bearings 60 may be of any suitable type, but should be designed so as to prevent lateral movement of the crucible carriage. The latter is countcrbalanced so as to facilitate raising and lowering thereof by the operator. in this connection it is to be noted that attached to the underside of bed 2 adjacent to slide rods and 12 are two like pulley support members 62 each carrying a rotatable pulley 64. Each pulley carries a like cable 66, one end of which is attached to carriage plate 58 and the other end of which is tiedto a counterweight 68. The latter balances the weight of carriage 56 so as to facilitate raising and lowering thereof by the operator and to hold it at a selected level. As an optional feature, locking means (not shown) may be employed to lock the carriage 56 at any desired height.

Mounted on the crucible carriage plate 56 is an elongate vertical frame 70 which is located and sized so as to move up and down within the opening 18 in bed 2. The upper end of the frame 70 has a plate 72 adapted to close off the bottom end of the furnace when brought into contact with mounting ring 44. Plate 72 has a vertical extension 74 adapted to support a crucible 76.

The rods 10 and 12 also serve as slide rods for a second carriage identified generally at 80 which forms part of the crystalpulling mechanism. This second carriage comprises a horizontal plate 82 provided with two openings at its sides which are fitted with sleeve bearings 84 that are mounted on the rods 10 and 12, with the result that the carriage 82 can move up and down along the two rods. The carriage plate 82 has affixed to its upper surface a bracket consisting of a vertically extending arm 86 and a horizontal plate 87 attached to the upper end of arm 84. Anchored to plate 87 is a cable 88 which forms part of a counterbalancing mechanism for the crystal-pulling carriage. This counterbalancing system includes a bracket 90 which is bolted to the top plate 18 and carries a horizontally extending arm 92 which is fitted at its ends with two pulleys 94 and 96. The cable 88 runs over the two pulleys 94 and 96 and extends down within a tube 98 which is attached to the sides of plates 18 and by releasable clamping brackets 100. Disposed within the tube 98 is a counterweight 102 to which the cable is attached. The counterweight 102 balances the weight of carriage 82 and the mechanism (hereinafter described) supported by the amount of power required to raise and lower the crystal-pulling mechanism.

The carriage plate 82 also has a hole 104 which is aligned with the center axis of the furnace 36. Hole 104 serves as a feedthrough hole for a crystal being pulled from a crucible mounted within the furnace. A second feedthrough hole 106 is provided in the top plate 18. In practice it is to be appreciated that when a continuous crystal is being grown, the pulling mechanism hereinafter described pulls the product through holes 52 and 104 and passes it through hole 106 to a suitable winding drum (not shown) on which it is wound. The means for winding up a continuous crystalline product forms no part of the present invention and, therefore, it is not believed necessary to describe the same, particularly in view of the fact that such mechanism is well known in the art.

The crystal-pulling mechanism which is supported by and includes carriage 80 comprises a drive assembly shown in FIGS. 3 and 4 and a gripping and pulling assembly shown in FIG. 5 and 6. Motorized movement of carriage 80 is accomplished by the drive assembly of FIGS. 5 and 6 in association with a vertically extending gear rack 110 which is attached by brackets 112 to the rear vertically extending rod 14 (see FIGS. 1 and 2). Turning now to FIGS. 1, 2, 3 and 4, the drive assembly comprises a front vertically extending mounting plate 114 which is bolted in place on the carriage plate 82, and two additional plates 116.and 118 which are located behind and spaced from the plate 1 14. The plate 114 has two holes to accommodate the reduced diameter front ends of two like tie rods 120. These tie rods are secured to the plate 114 by means of like pilot members 122 which fit into holes in plate 114 and screws 124 which are screwed into tapped holes formed in the front ends of the tie rods and the pilot members. The front ends of pilot members 122 have a reduced diameter so as to provide shoulders 126. The rear ends of tie rods 120 have tapped holes at their rear ends. Located between the plates 116 and 118 are like spacer sleeves 128. Plates 116 and 118 are tied together to form a rigid assembly with front plate 114 by means of a pair of bolts which pass through spacer sleeves 128 and screw into the tapped holes provided in the rear ends of tie rods 120. Attached to the bottom portion of the plate 118 is an auxiliary plate 132. The plate is attached to plate 1 18 by means of two or more bolts 136.

Mounted on the rear of plate 118 is a variable speed DC motor 138 which may but need not be reversible. Motor 138 has an output shaft which extends through an oversized hole in plate 118 and carries a pinion gear 140. Also attached to the rear side of plate 118 is an electromagnetic friction clutch 142 having an output shaft provided with a pinion gear 144 that meshes with the teeth on rack 110. The clutch also has an input shaft (not visible in the drawings) which extends through a suitable opening in plate 118 and carries a large gear 146 which meshes with the motor driven pinion gear 140. Also forming part of the drive mechanism is a second electromagnetic friction clutch-brake 148 which is attached to the front side of plate 116. Clutch-brake 148 has an input shaft which extends through an oversized hole in plate 116 and is provided with a gear 152 that meshes with the motor driven pinion gear 140. The output shaft of clutch-brake 148 is provided with a pinion gear 154 which meshes with a gear 182 carried by a shaft 176 which forms part of the crystal-gripping and pulling assembly described hereinafter.

Affixed to the rear side of front plate 114 is an electromagnetic brake 158. The electromagnetic brake is mounted on a through shaft whose front end extends through plate 114 and carries an operating handle 162. The rear end of shaft 160 carries a pinion gear 164 (see FlG. 4) which meshes with the teeth on rack 110.

lt is to be appreciated that clutch 142, clutch-brake 148 and brake 158 are conventional commercially available units and, therefore, a detailed description of the construction of each of these units is not believed necessary for the purpose of describing and understanding the present invention. It is believed sufflcient to state that when clutch 142 is deenergized it is disengaged so that motor 138 cannot drive pinion gear 144. Similarly when clutch-brake 148 is deenergized its clutch section is disengaged and its brake section is engaged, so that not only will its output shaft on which pinion gear 154 is mounted be disengaged from its input shaft, but additionally its output shaft and pinion 154 will be locked against rotation. As for brake 158, it is normally engaged and must be energized in order to be disengaged. Hence so long as brake 158 is deenergized, shaft 160 cannot turn and the carriage 80 cannot move up or down. When brake 158 is energized so as to disengage it the carriage can be moved either manually by rotating handle 162, or by operation of motor 138 and energization of clutch 142. By way of example but not limitation, clutch 142 may be a Dynamic Magnetic Clutch, Model WMC-l8l; clutchbrake 148 may be a Dynamic Magnetic Clutch/Spring Brake Model MCSB-l8; and brake 158 may be a Simplatrol Brake (spring applied) Model SAB-SO.

Turning now to FIGS. 5 and 6, the crystal gripping and pulling assembly comprises a plate which is provided with a pair of holes 172 and 174 located and sized so as to allow the plate 170 to be mounted on the front ends of the pilot members 122 mounted in plate 114, with the rear surface of plate 170 engaging the shoulders 126 on the pilot members. Plate 170 is held in place by capscrews (not shown) which screw into the pilot members.

Rotatably mounted in plate 170 in spaced side by side relation with each other are two shafts 176 and 178. Affixed to these shafts on the rear side of plate 170 are a pair of like spur gears 180. Although only one of these spur gears is shown (see FIG. 5) it is to be understood that they mesh with each other. Shaft 176 is longer than shaft 178 and its rear end is provided with a relatively large spur gear 182 adapted to mesh with pinion gear 154 mounted on the output end of clutch-brake 148. in this connection it is to be noted that plate 114 has a hole 184 (see FIGS. 1 and 3) which is oversized with respect to gear 182. Hole 184 permits gear 812 to be passed through plate 114 into meshing engatemcnt with pinion gear 154 when the gripping and pulling assembly is united with the drive assembly previously described. The front end of shaft 176 is provided with a handle 186 for turning shafts 176 and 178 manually. Also secured onto shafts 176 and 178 respectively are two like sprockets 188 and 190 provided with like sets of spaced teeth 192.

Also mounted in plate 179 so that they cannot rotate are two stub shafts 194 and 196 mounted below but in vertical alignment with shafts 176 and 178 respectively. Shafts 176 and 178 project forward of plate 170 and rotatably mounted thereon in coplanar relation with sprockets 188 and 190 (as seen in FIG. 5) are two additional sprockets 200 and 202. Means (illustrated but not identified) are provided to prevent axial movement of sprockets 200 and 202 on shafts 194 and 196. The latter also carry like arms 206 and 208 which are held on shafts 194 and 196 in spaced relation to sprockets 200 and 204 by suitably means, including snap rings 210. Arms 206 and 208 are free to rotate on shafts 194 and 196, except as limited by other associated means hereinafter described. Attached to the free ends of arms 206 and 208 are stub shafts 212 and 214 on which are rotatably mounted two additional sprockets 216 and 218 which are alike and are located in coplanar relation with the other sprockets previously described. Mounted on the sprockets 188, 200 and 216 is an endless belt 222. A like belt 224 is mounted on sprockets 190, 202 and 218. These endless belts are made of a suitable material which will not stretch readily, e.g. Mylar, and are provided with suitable spaced apertures to accommodate the sprocket teeth 192. Because of the positions of sprockets 188, 200, 190 and 202, each belt has a vertical run. The belts are maintained under tension by means of wire spring members 228 and 230 which are affixed to the ends of shafts 194 and 196 and at their other ends are bent over the arms 206 and 208. The leaf springs urge arms 206 and 208 to pivot clockwise and counterclockwise so that their sprockets 216 and 218 keep the belts under tension.

Plate 170 is provided with a pair of vertically spaced, horizontally extending grooves 230 which serve as guide channels for two slide blocks 232 and 234. The latter each have a pair of rails 238 shaped to fit in the grooves 230. Additionally the mutually adjacent ends of slide blocks 232 and 234 have angular extensions in the form of jaws 236 and 238 with flat confronting surfaces 340 and 242 which extend vertically. Blocks 232 and 234 are slidably secured to plate 170 by means of bolts 244. Both blocks have an elongated slot 246 through which the bolts extend and which allow the jaws to be moved horizontally, with the limit of travel of the two jaws being determined by the length of the slots. As seen in FIG. 5, the belts 222 and 224 and their supporting sprockets are spaced from plate 170 a distance sufficient so as not to interfere with sliding movement of blocks 232 and 234, except that the jaws 236 and 238 project forward enough so that their surfaces 240 and 242 are slidably engaged by and provide support for the vertical runs of belts 222 and 224.

Still referring to H68. 5 and 6, the bloc 232 is provided with a vertically extending hole in which is rotatably mounted a rod 248. The upper and lower ends of rod 248 have aligned eccentric extensions 250 and 252, with the former having a knob 254 at its extremity. A setscrew 255 in the side of block 232 serves to prevent rotation of rod 248. Attached to the extension 250 is one end of a tension spring 256. The opposite end of tension spring 256 is attached to a pin 258 which is mounted in and projects from the upper side of block 234. One end of a second tension spring 260 is attached to eccentric extensions 252. The opposite end of the tension spring 260 is attached to another pin 262 which projects from the bottom side of block 234. Also secured to the side of plate 170 adjacent block 234 by means of capscrews 264 is a plate 266. The latter projects forward of plate 170 in intercepting relation to block 234 and carries a bushing 270 in which is screwed a threaded member 272 having an axial extension in the form ofa pin 276 which projects through plate 266 and engages the adjacent side of the block 234. Plate 266 also is provided with two pins 278 and 280 at its upper and lower sides which serve as anchors for two additional tension springs 282 and 284 whose opposite ends are attached to the pins 258 and 262.

The foregoing assemblage of springs is designed to urge the two jaws 236 and 238 toward each other against belts 222 and 224, thereby holding the vertical runs of the two belts in tight gripping relation with a seed or filament which is interposed thcrebetween. Changing the rotational portion of rod 248 by loosening setscrew 255 and turning knob 254 changes the tension on the springs 256 and 260, causing the jaw 236 to be urged more or less strongly toward the jaw 238. Turning the threaded member 272 causes the pin 276 to be extended or withdrawn with respect to the block 234, thereby altering the force exerted by the springs 282 and 284 in opposition to the force exerted by spring 256 and 260 The net result is that the two jaws tend to be constantly centered and held in tight gripping relation with a seed or filament interposed thcrebetween.

Turning now to FIG. 7, the motor 138 is reversible and is connected to a suitable power supply 285 by way of a manually operable three position motor control switch 286 having stationary contacts 288 and 290 which are connected to the forward and reverse motion circuits respectively of the motor. Power supply 285 also is connected to manually operable three position control switch 292 having one stationary contact 294 connected directly to the energizing coil of brake 158 and a second stationary contact 296 connected by way of a normally closed limit switch 298 which is connected in series with the operating coil 300 ofa relay having a pair of normally closed contacts 302 and two pairs of normally open contacts 304 and 206. In FIG. 7 the relay contacts are shown in the position they occupy when coil 300 is energized. Contacts 302, 304 and 306 are connected to the energizing coils of belt clutch-brake 148, brake 158 and carriage clutch 142 respectively. Limit switch 298 is mounted so as to be opened automatically when the carriage has been raised to a predetermined level with respect to the furnace 36. Assuming that switch 292 is closed on its contact 296, opening of switch 298 will deenergize relay coil 300 to cause dccnergization of carriage clutch 142 and brake 158 and energization of belt clutch 148, with the result that the carriage 80 will stop and belts 222 and 224 will start moving. Limit switch 298 can be mounted on any suitable support, e.g. one of the rods 10, 12 and 14 or the top plate 18, in position to be actuated by carriage plate 82 or pulley bracket member 86 or some other member carried by the crystal-pulling mechanism, and it is believed to be obvious that the mounting means for the limit switch can be adapted to permit adjustment of its height so as to vary the height at which the carriage 80 is stopped.

Operation of the apparatus just described is straightforward and is as follows. Initially the operator lowers the crucible carriage 56 so that the top plate 72 of the crucible support frame 70 is below the bed 2. Then a crucible containing the source material from which the crystal is to be grown is mounted on the support 70 and the carriage 56 is raised until the crucible is located within the furnace 36. Thereafter the coil 38 is energized to heat the crucible and convert its contents to a melt. With the melt established, the operator mounts a seed to the pulling mechanism. This is achieved by turning the eccentric knob 254 and the threaded member 272 to relieve the pressure exerted on blocks 232 and 234 by springs 252, 260, 282 and 284, placing the seed between belts 222 and 224 and then turning knob 254 and threaded member 272 until the jaws 236 and 238 exert sufficient pressure on the belts to cause them to firmly grip the seed. The seed is disposed so that a substantial portion thereof projects below carriage 80. Thereafter the carriage is lowered to position the seed in the furnace in contact with the melt. This lowering operation is accomplished manually by means of handle 162 after first closing switch 292 with respect to its contact 294 so as to disengage brake 158 and prevent engagement of clutch 142 and the clutch section of clutch,brake 148. With brake 158 disengaged, the pinion 164 can be turned by handle 162 to lower the carriage 80 to the desired level. Thereafter switch 292 is closed with respect to its its contact 296. Since limit switch 298 is closed when the carriage is down next to the furnace, relay coil 300 now will be energized and contacts 302, 204 and 306 will be in the posi tion shown in FIG. 7. Accordingly, brake 142 will be disengaged, carriage clutch 142 will be engaged and the clutch section of clutch-brake 148 will be disengaged while its brake section will be engaged. Motor switch 286 is now closed on its contact 288 to cause motor 138 to operate in the forward direction. The motor operates through clutch 142 to rotate pinion gear 144 along rack 110 so as to raise the carriage and pull the growing crystal (shown schematically in FIG. 1 by the line C) at a constant speed determined by the setting of motor 138 and the ratios of gears 140, 146 and 144. The belts cannot move because pinion 154 is locked by the brake section of clutch-brake 148. At a point in the path of travel of carriage 80 determined by the location of limit switch 298, limit switch 298 is opened to deenergize relay coil 300, thereby causing the contacts 304 and 306 to open and the contacts 302 to close. When this occurs carriage clutch 142 and brake 148 are dcencrgized and the clutch section of belt clutch-brake 148 is energized. This results in stopping of the carriage and rotation of the output gear 154 of clutch-brake 148 which in turn drives the belts 222 and 224 through gears 180 and the sprockets 188 and 190. The latter rotate clockwise and counterclockwise respectively, thereby causing the endless belts to move in the direction indicated by the arrows in FIG. 6. The resultant movement of the belts upwardly between the two jaws 236 and 238 pulls the crystalline product C upwardly away from the crucible. The gearing is arranged so that the belts pull the filament at the same speed that is was pulled by movement of the carriage. Once the belts have been actuated, the process is substantially continuous until the motor 138 is decnergized, or switch 292 is opened with respect to both its contacts 292 and 296, or the supply of material in the crucible is exhausted.

FIGS. 8, 9 and 10 show an alternative modification of the dual belt crystal gripping and pulling assembly. In this case two fixed blocks 310 and 312 are attached to the plate 170 by means of suitable capscrews 314. The blocks are spaced one from the other so as to accommodate the vertical runs of the two belts 222 and 224 as shown. Each of the blocks is formed with a cavity 316 along the face thereof which confronts the other block. The face of each block is covered by a removable plate 318 which has one or more slots 320. Preferably these plates are made of a low-friction material such as Teflon. The plates are attached to the blocks by means of suitable screws 324. Each block also is fitted with a bushing 326 which serves as the connector for an airhose 328 which leads to a suitable supply of air at a regulated pressure (not shown). Air is introduced to the blocks via the hoses and leaves the blocks via the cavities 316 and the slots 320, with the result that a stream of air is directed at the belts to urge the vertical runs thereof into tight engagement with the filament which is being pulled from the melt. It is believed clear that this modification is similar to the modification illustrated in FIGS. 5 and 6 in the sense that the blocks serve to limit the maximum gap between the vertical runs of the two belts and the two belts are constantly urged toward each other to grip the crystal issuing from the melt.

As made clear by the foregoing description a crystal-pulling mechanism constructed in accordance with this invention is capable of two alternative modes of operation. In the one mode the carriage moves and the two belts are stationary with respect to each other, so that pulling of the seed or growing filament is achieved by movement of the carriage. In the other mode, the carriage is stationary and the belts are driven, so that the or filament is pulled by movement of the belts rather than movement of the carriage. Because of this alternative mode of operation which may be made sequential as described above, the apparatus may be used to grow crystal shapes of relatively short or indefinite lengths. When relatively short crystals are to be pulled, the crystals are pulled solely by movement of the carriage. On the other hand, when continuous filaments or ribbons are to be grown, pulling is achieved solely by moving the belts or moving the belts in sequence with movement of the carriage. Having two modes of operation offers two advantages. First of all, it may not be possible to start with a previously grown seed of substantial length, in which case it is necessary to locate the seed-gripping means close to the furnace. This requirement is met by virtue of the fact that the carriage is moveable and can be lowered very close to the furnace. Secondly, if the seed or growing crystal is not perfectly straight or if it is slightly askew with respect to the axis of travel of the vertical runs of the belts, its bottom end will tend to wiggle as it is being pulled by movement of the belts. This effect is particularly noticeable when growing relatively small diameter filaments, e.g. filaments with a diameter of about five-thousandths of an inch. The shorter the filament or seed, the more critical is the wiggling since the lateral forces of the filament or seed with respect to the melt at the growth interface caused by the wiggling are directly proportional to the length of the filament or seed between the carriage and the growth interface. If this length isrelatively short, the lateral forces are often sufficient to overcome the surface tension of the melt and hence the end of the filament or seed will tend to move laterally and thereby break free of the melt or grow crooked. This problem is minimized by initially pulling by movement of the carriage rather than by movement of the belts. Movement of the carriage does not produce any wiggle and the crystal growth occurs along the path of movement of the carriage. When the crystalline product has gown to a substantial length, the belts may be used for pulling since now any wiggle effect seen at the growth interface is insufficient to overcome the surface tension of the melt. Hence the wiggling will not cause the growing crystal to break free of the melt and the crystal will grow straight. The invention offers the further advantage that it is capable of pulling a variety of shapes from a melt, including but not limited to round filaments and ribbons. The invention has been employed in growing sapphire filaments and ribbons which are useful as reinforcing elcments for metal matrices. It also may be used to grow materials other than sapphire.

It is also believed appreciated that the invention herein described is capable ofmany variations and modifications, depending upon the types of materials to be grown and the conditions essential to sustaining continuous growth. Accordingly the invention is to be limited solely by the following claims.

What is claimed is:

1. Apparatus for pulling an extended crystalline body from a melt comprising a carriage, means supporting said carriage for vertical movement, crystal-gripping means carried by said carriage, said crystal-gripping means including a pair of endless belts, means carried by said carriage mounting said endless belts so that each belt has a vertically extending run with the vertical run of one belt disposed adjacent to the vertical run of the other belt so as to grip a crystalline body interposed therebetween, first drive means for raising said carriage, second drive means for moving said belts so that they move upwardly along said vertically extending run, and control means for selectively operating said first and second drive means.

2. Apparatus as defined by claim 1 further including means for selectively causing said control means to operate said first drive means to raise said carriage a selected distance and then to deactivate said first drive means and activate said second drive means so that a crystalline body gripped by said belts is pulled first by movement of said carriage and then by movement of said belts.

3. Apparatus according to claim I wherein said means supporting said carriage for vertical movement comprises at least two vertically extending guide rods, and further including a bed plate through which said guide rods extend, and releasable clamp means carried by said bed plate for releasably locking said guide rods to said bed plate.

4. Apparatus according to claim 1 wherein said first drive means comprises a stationary vertically extending gear rack and means including a gear in engagement with said rack and carried by said carriage driving said gear along said rack so as to move said carriage vertically at a rate determined by the rate of travel of said gear along said rack.

5. Apparatus according to claim 1 wherein said first and second drive means includes first and second clutches, and

further wherein said control means includes means for selectively operating said clutches.

6. Apparatus according to claim 1 further including means for urging said vertical belt runs toward each other whereby to maintain said belts in tight gripping relation with an elongate crystalline body interposed between said vertical runs.

7. Apparatus for the continuous growth of a crystalline material from a melt comprising means for supporting a crucible for containing a melt of said material, heating means for controlling the temperature of a melt of said material contained in a crucible supported by said support means, a carriage means mounting said carriage for reciprocal vertical movement above a crucible supported by said support means, selectively operable first drive means for moving said carriage upwardly relative to a crucible supported by said support means, first and second sprocket means carried by said carriage, first and second endless belts mounted for endless movement on said first and second sprocket means respectively with the path of movement of each belt including a vertical run, the vertical run of said second belt being adjacent to but spaced horizontally from the vertical run of said first belt, said belts also being mounted so that the space between their vertical runs is aligned with a crucible supported by said support means, for urging the vertical runs of said belts toward each other so as to grip therebetween an elongate crystal issuing from said crucible, selectively operable second drive means connected to said sprocket means for causing movement of said belts so that said vertical runs are upward, and means for selectively operating said first and second drive means.

8. Apparatus according to claim 7 further including means for preventing movement of said belts when said carriage is being moved by operation of said first drive means.

9. Apparatus according to claim 7 further including selectively disengageable brake means adapted when engaged to lock said carriage against vertical movement.

10. Apparatus according to claim 9 further including means for disengaging said brake means when said first drive means is operated and reengaging said brake means when said second drive means is operated.

11. Apparatus according to claim 7 wherein said first drive means comprises a rack and pinion mechanism.

12. Apparatus according to claim 11 wherein said rack and pinion mechanism comprises a stationary vertically extending rack and a pinion gear which travels along said rack, and further wherein said first drive means includes powered means carried by said carriage for rotatably driving said pinion gear along said rack.

13. Apparatus according to claim 12 further including a motor carried by said carriage, and further wherein said powered means includes a drive gear driven by said motor and coupled to said pinion gear.

14. Apparatus according to claim 13 further including a selectively releasable clutch connected between said drive gear and said pinion gear.

15. Apparatus according to claim 13 wherein said second drive means is connected to and powered by said motor.

16. Apparatus according to claim 7 wherein said second drive means includes a selectively engageable clutch.

17. Apparatus according to claim 7 further including means for counterbalancing said carriage.

18. Apparatus for pulling an extended crystal from a melt comprising a horizontal bed, means supporting said bed, a fur nace mounted on said bed, said furnace having a chamber with an opening at its top end for withdrawing a crystalline body issuing from a melt in said chamber, an elongate guide structure for a carriage extending up from said bed, means releasably clamping said guide structure in fixed relation to said bed, and a crystal-pulling mechanism for pulling a crystal issuing from a melt in said chamber, said crystal-pulling mechanism comprising a carriage slidably mounted on said guide structure for reciprocal vertical movement relative to said bed, means for raising and carriage along said guide structure, and crystal-gripping means mounted on said carriage for pulling a crystalline body from a melt contained in said fur nace chamber, said crystal-gripping means including horizontally opposed first and second resilient means and pressure-exerting means for forcing said first and second resilient means into tight gripping relation with a crystalline body interposed between said resilient means.

19. Apparatus according to claim 18 wherein said first and second resilient means are portions of first and second endless belts.

20. Apparatus according to claim 19 wherein said pressureexerting means comprise first and second movable jaws which bear against said endless belt portions.

21. Apparatus according to claim 19 wherein said pressureexerting means comprise means for directing a pressurized fluid against said endless belt portions.

22. Apparatus according to claim 18 further including means supporting said belts and defining endless paths of movement for said belts, said endless paths including vertical runs and said portions constituting at least part of said endless runs, and means for preventing movement of said belts along said endless paths while said carriage is moving along said guide structure.

23. Apparatus according to claim 22 further including drive means for causing movement of said belts along said endless paths while said carriage is stationary, whereby to effect pulling of said issuing crystalline body by said belts while said carriage is stationary.

24. Apparatus according to claim 18 wherein said chamber has an opening at its bottom end for introduction of a crucible for containing said melt, a crucible carriage below said bed, and means mounting said crucible carriage for movement toward and away from said bed.

25. Apparatus according to claim 24 further including means for counterbalancing said crucible carriage.

26. A mechanism for pulling a continuous crystal issuing from a melt contained in a crucible, said mechanism comprising a carriage having crystal-gripping means, means supporting said carriage for vertical movement, selectively operable drive means for raising said carriage so as to effect pulling of a crystal gripped by said gripping means, said crystal-gripping means comprising a pair of endless belts, means on said carriage mounting said belts for movement along endless paths with each path having a vertical leg, said vertical legs being adjacent to but spaced from each other, selectively operable drive means for moving said belts along said endless paths so as to move in an upward direction along said vertical legs, means for pressing those portions of said belts travelling along said vertical legs into gripping relation with a crystal interposed between said legs, and means for selectively operating one or the other of said carriage and belt drive means so that a continuous crystal issuing from a melt and gripped by said belts may be pulled by raising said carriage or moving said belts.

27. Apparatus according to claim 26 wherein said carriage and belt drive means are adapted to raise said carriage and move said belts at substantiallythe same speed.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3 6O7,ll2 Dated September 21, 1971 fls) Seymour Mermelstein It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 7, Column 9 Line 22, before "means" insert a Claim 7, Column 9, Line 34, after the and before "for" insert -means-.

Signed and sealed this 7th da of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Attestina, Officer ROBERT GOTTSCHALK Commissioner of Patents DRM PO-1050 (10-69} USCOMM-DC B0375-P69 U 5, GOVERNMENT PRINTING OFFICE I969 0-36533fi 

2. Apparatus as defined by claim 1 further including means for selectively causing said control means to operate said first drive means to raise said carriage a selected distance and then to deactivate said first drive means and activate said second drive means so that a crystalline body gripped by said belts is pulled first by movement of said carriage and then by movement of said belts.
 3. Apparatus according to claim 1 wherein said means supporting said carriage for vertical movement comprises at least two vertically extending guide rods, and further including a bed plate through which said guide rods extend, and releasable clamp means carried by said bed plate for releasably locking said guide rods to said bed plate.
 4. Apparatus according to claim 1 wherein said first drive means comprises a stationary vertically extending gear rack and means including a gear in engagement with said rack and carried by said carriage driving said gear along said rack so as to move said carriage vertically at a rate determined by the rate of travel of said gear along said rack.
 5. Apparatus according to claim 1 wherein said first and second drive means includes fiRst and second clutches, and further wherein said control means includes means for selectively operating said clutches.
 6. Apparatus according to claim 1 further including means for urging said vertical belt runs toward each other whereby to maintain said belts in tight gripping relation with an elongate crystalline body interposed between said vertical runs.
 7. Apparatus for the continuous growth of a crystalline material from a melt comprising means for supporting a crucible for containing a melt of said material, heating means for controlling the temperature of a melt of said material contained in a crucible supported by said support means, a carriage means mounting said carriage for reciprocal vertical movement above a crucible supported by said support means, selectively operable first drive means for moving said carriage upwardly relative to a crucible supported by said support means, first and second sprocket means carried by said carriage, first and second endless belts mounted for endless movement on said first and second sprocket means respectively with the path of movement of each belt including a vertical run, the vertical run of said second belt being adjacent to but spaced horizontally from the vertical run of said first belt, said belts also being mounted so that the space between their vertical runs is aligned with a crucible supported by said support means, for urging the vertical runs of said belts toward each other so as to grip therebetween an elongate crystal issuing from said crucible, selectively operable second drive means connected to said sprocket means for causing movement of said belts so that said vertical runs are upward, and means for selectively operating said first and second drive means.
 8. Apparatus according to claim 7 further including means for preventing movement of said belts when said carriage is being moved by operation of said first drive means.
 9. Apparatus according to claim 7 further including selectively disengageable brake means adapted when engaged to lock said carriage against vertical movement.
 10. Apparatus according to claim 9 further including means for disengaging said brake means when said first drive means is operated and reengaging said brake means when said second drive means is operated.
 11. Apparatus according to claim 7 wherein said first drive means comprises a rack and pinion mechanism.
 12. Apparatus according to claim 11 wherein said rack and pinion mechanism comprises a stationary vertically extending rack and a pinion gear which travels along said rack, and further wherein said first drive means includes powered means carried by said carriage for rotatably driving said pinion gear along said rack.
 13. Apparatus according to claim 12 further including a motor carried by said carriage, and further wherein said powered means includes a drive gear driven by said motor and coupled to said pinion gear.
 14. Apparatus according to claim 13 further including a selectively releasable clutch connected between said drive gear and said pinion gear.
 15. Apparatus according to claim 13 wherein said second drive means is connected to and powered by said motor.
 16. Apparatus according to claim 7 wherein said second drive means includes a selectively engageable clutch.
 17. Apparatus according to claim 7 further including means for counterbalancing said carriage.
 18. Apparatus for pulling an extended crystal from a melt comprising a horizontal bed, means supporting said bed, a furnace mounted on said bed, said furnace having a chamber with an opening at its top end for withdrawing a crystalline body issuing from a melt in said chamber, an elongate guide structure for a carriage extending up from said bed, means releasably clamping said guide structure in fixed relation to said bed, and a crystal-pulling mechanism for pulling a crystal issuing from a melt in said chamber, said crystal-pulling mechanism comprising a carriage slidably mounted on said guide structurE for reciprocal vertical movement relative to said bed, means for raising and carriage along said guide structure, and crystal-gripping means mounted on said carriage for pulling a crystalline body from a melt contained in said furnace chamber, said crystal-gripping means including horizontally opposed first and second resilient means and pressure-exerting means for forcing said first and second resilient means into tight gripping relation with a crystalline body interposed between said resilient means.
 19. Apparatus according to claim 18 wherein said first and second resilient means are portions of first and second endless belts.
 20. Apparatus according to claim 19 wherein said pressure-exerting means comprise first and second movable jaws which bear against said endless belt portions.
 21. Apparatus according to claim 19 wherein said pressure-exerting means comprise means for directing a pressurized fluid against said endless belt portions.
 22. Apparatus according to claim 18 further including means supporting said belts and defining endless paths of movement for said belts, said endless paths including vertical runs and said portions constituting at least part of said endless runs, and means for preventing movement of said belts along said endless paths while said carriage is moving along said guide structure.
 23. Apparatus according to claim 22 further including drive means for causing movement of said belts along said endless paths while said carriage is stationary, whereby to effect pulling of said issuing crystalline body by said belts while said carriage is stationary.
 24. Apparatus according to claim 18 wherein said chamber has an opening at its bottom end for introduction of a crucible for containing said melt, a crucible carriage below said bed, and means mounting said crucible carriage for movement toward and away from said bed.
 25. Apparatus according to claim 24 further including means for counterbalancing said crucible carriage.
 26. A mechanism for pulling a continuous crystal issuing from a melt contained in a crucible, said mechanism comprising a carriage having crystal-gripping means, means supporting said carriage for vertical movement, selectively operable drive means for raising said carriage so as to effect pulling of a crystal gripped by said gripping means, said crystal-gripping means comprising a pair of endless belts, means on said carriage mounting said belts for movement along endless paths with each path having a vertical leg, said vertical legs being adjacent to but spaced from each other, selectively operable drive means for moving said belts along said endless paths so as to move in an upward direction along said vertical legs, means for pressing those portions of said belts travelling along said vertical legs into gripping relation with a crystal interposed between said legs, and means for selectively operating one or the other of said carriage and belt drive means so that a continuous crystal issuing from a melt and gripped by said belts may be pulled by raising said carriage or moving said belts.
 27. Apparatus according to claim 26 wherein said carriage and belt drive means are adapted to raise said carriage and move said belts at substantially the same speed. 